| 摘要 |
PURPOSE:To reduce the variation of gain by using a feedback circuit passing a source follower from the output terminal of a one-stage differential amplifier to perform the feedback to the negative-polarity input terminal of the one-stage differential amplifier and using the gain reduction due to the source follower to reduce the feedback quantity. CONSTITUTION:When mutual conductances of transistors (TR) 2 and 4 are set equally to GM4 and output conductances of TRs 4, 7, and 9 are denoted as G4, G7, and G9 respectively, deviation (reduction) DELTAG1 of the gain of an amplifier circuit 11 from 1 is expressed with formula DELTAG1=(G4+G7+G9)/GM4. Meanwhile deviation DELTAGF of the gain of a source follower 20, namely, the gain from an output terminal 3 to the gate of the TR4 from 1 is expressed with formula DELTAGF=(GE+GC)/GMF where the mutual conductance of the TR 20 is denoted as GMF and output conductances of TRs 20 and 27 are denoted as GE and GC. Consequently, DELTAGF=DELTAG1 is necessary for the purpose of compensating deviation of the gain of the amplifier circuit 11 from 1 with reduction of the feedback quantity due to the source follower. Therefore, gate lengths of TRs 7, 9, and 27 are extended, and gate lengths and operating current densities of TRs 4 and 20 are equalized.
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